Document processing devices are effective tools for processing documents of various types. For example, mail processing facilities often employ a multitude of document processing devices to process letters, packages, envelopes, coupon booklets, brochures, post cards and other mail items intended for distribution via a mail distribution network (e.g., the United States Postal Service (USPS)). The types of devices employed may include high-speed sorters for sorting mail items according to a sort scheme, high-speed inserters for inserting documents that comprise a mail item, cutters, printers, accumulators and folders for generating, assembling, arranging and organizing mail items in connection with a sorter or inserter, mail bins for accumulating the multitude of mail items processed in preparation for distribution, etc. Whether used independently or in combination, the aforementioned document processing devices must be able process documents at very high speeds with sufficient accuracy along a transport path. Consequently, it is not uncommon for such devices to stage one or more imaging devices along the transport path to capture images of a mail item as it is processed.
Commonly, imaging devices integrated within a document processing device are used in connection with an object character recognition or barcode reader utility to perform address verification or validation, wherein the address components and/or delivery point identifiers printed upon a mail item are checked for accuracy and compliance with postal authority regulations or sort processing, wherein again the address components and/or delivery point identifiers printed upon a mail item act as input to a sort scheme that informs a sorter's processing decisions. In other instances, images of a mail item may be maintained for qualitative analysis, error checking, sequence verification, barcode integrity, address cleansing, data mining, machine control, item tracking and other forms of examination useful for ensuring a mail item is generated or sorted to garner the maximum postal authority discounts. The frequency of image capture occurring during mail item transport through a high-speed document processing device will depend greatly on the types of and extent of analysis required to be performed to render a high quality mail item. For the most part, greater frequency of imaging of a mail item through a document processing device results in enhanced mail quality given that the mail item is progressively viewed throughout processing.
Of course to achieve such capability, typical document processing devices employ high speed imaging devices (cameras). While effective for imaging transported documents as they traverse through the document processing device at high speeds, the frequency, or rather, potential points of image capture is limited. This is due in large part to the physical and functional requirements of such cameras, which tend to be of a form factor not befitting often condensed areas where imaging may be desired. For instance, a desired point of image capture within the document processing device may be the point of contact of the document with the primary transport belt in a sorting device, at the output channel of a printer within a printer or high speed print inspection system, or at the point of document collating or assembly within an inserting device. Typical high speed imaging devices are not well suited physically for accommodating image capture in such tight areas of the document processing device.
Also, from a functional standpoint, typical high speed cameras are limited in that they must be positioned at a fixed depth or in accord with a specified imaging range/area in order to enable effective image capture during high speed transport. This is due to the fact that that they rely upon optical imaging techniques, area based scanning requirement, etc. for image capture. This may include a required offset distance from the camera to the target for enabling two-dimensional image capture. Also, this may include usage of varying lenses, mirrors and other devices for transmitting sensed image data to the camera sensors during transport—a requirement that for a typical document processing device limits camera placement and hence image capture frequency and opportunity. Such limitations as described above especially limit effective throughput of the device as well as full scanning of a document without reductions in speed.